Friction and wear of PTFE composites in hydrogen under high temperature and high sliding speed condition

Transcription

1 Friction and wear of PTFE composites in hydrogen under high temperature and high sliding speed condition Takehiro Morita 1,4,Yoshitaka Naganuma 2,Yoshinori Sawae 1,4,Kazumi Okada 3 Yoshie Kurono 3,Joe Kaneuchi 5,Hiroyoshi Uesjima 5,Joichi Sugimura 1,3,4 1 Department of Mechanical Engineering, Kyushu University 2 Graduate School of Engineering, Kyushu University 3 Research Center for Hydrogen Industrial Use and Storage, AIST 4 International Institute for Carbon-Neutral Energy Research, Kyushu University 5 STARLITE Co., Ltd, Japan

2 Objectives PTFE and PTFE composites are preferably used as a material for dynamic seals in control valves because it can keep the friction coefficient very low even the under unlubricated conditions. On the other hand, PTFE exhibits poor wear resistance. The wear characteristics of PTFE can be improved significantly by adding filler materials. A direct filling method is going to be adopted in the real hydrogen station. Therefore conditions of use of seal materials become more severe. However, there are little report under higher temperature and higher sliding speeds conditions in hydrogen. In this study Examine the effect of filler materials on friction and wear in hydrogen under high temperature and high sliding speed condition.

3 Specimens Pin specimen Material: Unfilled PTFE (PTFE) 20wt% Glass Fiber filled PTFE (GF) 20wt% Carbon Fiber(Pitch) filled PTFE(CF1) 20wt% Carbon Fiber(Pan) filled PTFE(CF2) 20wt% Poly Phenylene Sulfide filled PTFE (PPS) Dimension: Diameter = 6mm, Length = 15 mm Disk specimen Material: Gray Cast Iron FC250 Dimension: Diameter = 56mm, Thickness = 3 mm Test specimens shapes φ6 15 Surface hardness: 241Hv Surface roughness: Ra=0.1μm Pin φ56 Disk t3

4 Test rig & Test conditions Displacement sensor Dead load Oxygen sensor Water sensor Test apparatus Pin Disk Gas outlet Friction sensor Load sensor Turbo molecular pump Scroll pump Gas inlet Gas filters Motor Test conditions Load 28.3 N (pressure 1 MPa) Speed 2000mm/sec Sliding distance 40000m (Running-in distance 10000m) Temperature 373K Gas Hydrogen,Argon,Air Lubrication Dry

5 Friction and wear in hydrogen X10 1.E 03 3 Coefficient of friction GF PPS PTFE CF1 CF Sliding distance [m] Specific wear rate [mm 3 /Nm] 1.0X10 1.E X10 1.E X10 1.E X10 1.E X10 1.E 08 8 PTFE GF CF1 CF2 PPS Comparison of friction coefficient with sliding distance in hydrogen Comparison of specific wear rate of pins in hydrogen Wear of pin in unfilled PTFE was excessive. All of composites decrease the specific wear rate of pins. Coefficient of friction in hydrogen were different with filler composites.

6 Wear surface & wear of disk in hydrogen Pin Disk PTFE GF CF1 CF2 Laser microscopic images of pins and disks wear surfaces in hydrogen PPS 0.1mm 1.4 Wear amount of disks [mg] Pins surface of GF and CF1filled PTFE found fillers flake off. In GF filled PTFE, abrasive wear were observed at disk surface and the wear of disk was larger. 0 PTFE GF CF1 CF2 PPS Comparison of specific wear rate of disks in hydrogen

7 Effect of gas types Coefficient of friction CF1 PPS H2 Ar Air H2 Ar Air Sliding distance [m] Specific weare rate [mm 3 /Nm] 1.0X10 1.E X10 1.E X10 1.E 07 7 H2 Ar Air H2 Ar Air CF1 PPS Coefficient of friction Comparison of friction coefficient with sliding distance in hydrogen, argon and air Comparison of specific wear rate of pins and final average of friction coefficient in hydrogen, argon and air In PPS filled PTFE, friction and wear were not affected by the kind of the gas. In CF1 filled PTFE, friction was lowest but wear was largest in hydrogen.

8 Summary Sliding tests were conducted under high temperature and high speed sliding speed conditions in hydrogen, argon and air. Unfilled PTFE could not use this condition. Both CF1 and PPS filled PTFE exhibited a good performance in hydrogen. GF filled PTFE could not have benefit on the wear of the disk. Friction and wear were influenced by the kind of gas types in CF1 filled PTFE, although in PPS filled PTFE were not influenced. Acknowledgements This study was conducted as a part of the Fundamental Research Project on Advanced Hydrogen Science through administration by NEDO.